Methods: A randomized controlled trial will be conducted in 10 out-patient clinics in Hong Kong. Subjects in the intervention group will receive a brief intervention on smoking reduction plus a smoking reduction leaflet. Additionally, subjects will be asked to think about a smoking reduction schedule for themselves after the negotiation with the counsellor. Subjects in the control group will receive a brief advice on quitting plus a leaflet on smoking cessation. Four consecutive (1, 3, 6 and 12 months) follow-ups will be conducted. The primary outcome measure is biochemically validated abstinence at 6 months. Secondary outcomes are: (i) biochemically validated abstinence at 12 months, (ii) self-reported 7-day point prevalence of abstinence at 6 and 12 months, (iii) self-reported reduction of ≥ 50% in cigarette consumption at 6 and 12 months, and (iv) self-efficacy against tobacco at 6 and 12 months.